QuantiFERON®-TB Gold Plus

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Turnaround Time: 2 - 5 days
CPT Code:


Test Type: 1 mL x four tubes in QuantiFERON-TB Gold Plus kit


QuantiFERON-TB Gold Plus is an in vitro diagnostic test using a peptide cocktail of CD4+ and CD8+ T cell antigens to stimulate cells in heparinized whole blood. Detection of interferon-gamma by enzyme-linked immunosorbent assay (ELISA) is used to identify in vitro responses to these peptide antigens that are associated with Mycobacterium tuberculosis infection. QuantiFERON-TB Gold Plus is an indirect test for M. tuberculosis infection (including disease) and is intended for use in conjunction with risk assessment, radiography, and other medical and diagnostic evaluations.

A negative QFT-Plus result does not preclude the possibility of M. tuberculosis infection or tuberculosis disease: false negative results can be due to stage of infection, co-morbid conditions that affect immune function, incorrect handling of the blood collection tubes following venipuncture, incorrect performance of the assay, or other individual immunological variables. Heterophile antibodies or non-specific interferon-gamma production from other inflammatory conditions may mask specific responses to CD4+ and CD8+ T cell antigens. A positive QFT-Plus result should not be the sole or definitive basis for determining infection with M. tuberculosis. Incorrect performance of the assay may cause false-positive results. A positive QFT-Plus result should be followed by further medical evaluation for active tuberculosis disease.

Collection Details:

Collection Instructions:

QuantiFERON is time-sensitive and specimens must be received in the laboratory within 14 hours of collection. Specimen collection times will vary depending on logistics from the blood draw location to a LabCorp lab. This test requires a special collection kit that may not be available at all PSCs.

To submit QuantiFERON specimens that are client-incubated, order QuantiFERON®-TB Gold Plus (Client Incubated) (Test No. 182893).

The QuantiFERON®-TB Gold Plus collection kit contains the instructions for the collection and handling of (one each): (1) gray-top (with white ring), uncoated (nil); (2) green cap with white ring, TB1 tube; (3) yellow cap with white ring, TB2 tube; (4) purple top with white ring, mitogen-coated. A high-altitude kit is also available for locations between 3350 and 6150 feet; a cap with a yellow ring differentiates the tubes.

Blood collection tubes should be at room temperature at the time of collection. Refer to collection instructions included with draw kit. Special specimen collection kit contains four gel-barrier tubes as noted above. All four tubes are required for a single test result. Each tube is designed to draw only 1 mL and fill time may be longer than other blood collection tubes. Because of the limited vacuum in these tubes, use a needle and holder (not a butterfly) to collect QuantiFERON® specimens. If a butterfly is required, first collect other required tubes or use another Vacutainer® tube to purge the butterfly line of air and then proceed with drawing the QuantiFERON tubes. Fill tubes to the black fill line on the tube. If tubes are underfilled or overfilled (see kit insert), immediately collect a replacement tube.

Following proper fill, label the tubes appropriately and shake tubes 10 times firmly enough to ensure the entire surface of the tube is coated with blood cells to solubilize the antigen on the tube walls. After shaking, the volume may fall below the fill line. Do not centrifuge or refrigerate specimens.

Return each of the four properly filled, labeled, and shaken tubes to the box labeled "QFT kit." Seal the top by removing tape from the adhesive. To preserve cellular viability, specimens should be collected and sent the same day, at room temperature, so as to arrive at the lab as soon as possible and within 14 hours of collection.

Maintain specimen at room temperature for four tube collection kit. Stability: Kit must be incubated within 16 hours of collection.